Typhoid Vaccination

This is a prospective closed cohort, open-label, phase III effectiveness study using a test-negative design of a typhoid conjugate vaccine, ZyVac® TCV (purified Vi capsular polysaccharide of Salmonella Typhi conjugated to tetanus toxoid as carrier protein), manufactured by Zydus Lifesciences Limited. The study will be conducted in a closed cohort population among children aged 6 months to 15 years residing in wards 5, 6, 7, 48, 49, 50, 63, 71, and 72 of Dhaka South City Corporation (DSCC). The targeted number of age-eligible children in the study area is \~92,000 among them \~60,000 will be vaccinated. A subset of the first 600 consenting participants will be selected by age strata (6 months to \<2 years, 2-4 years, 5-15 years) for enrollment in the immunogenicity study with an additional three follow-up visits. Diary cards will be used to collect adverse events (AEs) following immunization (AEFI) data up to day 7 for a subset of active follow-up of the first 600 vaccinated participants. Participants not in this subset will be encouraged to go to the 'Adverse Event Monitoring Cell' at the Maniknagar field office. Data on serious adverse events (SAEs) will be reported for six months after vaccination. All study updates including AEs and SAEs will be reported to the data safety and monitoring board (DSMB) and sponsor. Passive surveillance for typhoid fever will be carried out in the Maniknagar field office and Mugda Medical College and Hospital in the catchment area among the age-eligible children.